To dislodge Cameron from power, the Left needs fresh ideas and a vision of
Britain's future, writes Mary Riddell.

Like Monty Python's parrot, the Left needs urgent diagnosis. Is it dead or merely resting? David Miliband, one of several senior figures to make speeches with undertones of an autopsy report, has asked whether social democracy is in check or in checkmate. Today, Ed Miliband's consigliere, Lord Stewart Wood, will speak at the launch of a Fabian pamphlet entitled, gloomily, Europe's Left In Crisis.

Although the tone of the current ruminations is meant to be constructive, they are loaded with existential angst. If Labour is indeed expiring, it will not be a lonely demise. The French and Danish Left haven't sniffed power in a decade, Sweden's and Germany's social democrats are in free fall, and the Italian Left remains crushed beneath Berlusconi's Gucci loafer.

But even in this lacklustre company, the omens seem grim for the British Labour party, whose defeats in 1931, 1951 and 1979 were followed by many years in the wilderness. As Douglas Alexander, the shadow foreign secretary, said at the weekend, victory at the next election would mean "winning three times faster than at any time in our history".

Although a dead cat bounce is possible, Alexander is under no illusion about the effort real recovery would involve. David Miliband, in his bravura speech at the LSE, set out in brutal detail the ambush of the Left by a European Right redeemed by its embrace of compassionate conservatism.

Although Ed M told me that he thought his brother had supplied "a very, very good analysis", Labour runs the risk of believing its own posturing about an incompetent and malign Coalition led by a bullying PM, his hapless lieutenant and a rapacious Chancellor. Excessive cuts may (and should) prove the Government's undoing, but, for now, branding Cameron, Clegg and Osborne as Flashman, Bagman and Axeman is a parody.

Cameron may not be the Mother Teresa of politics, but his social liberalism has stationed him, in many voters' eyes, in the benevolent centre. True, he has made abysmal decisions, necessitating U-turns on selling off forests, withdrawing free school milk for poorer children and scrapping ring-fenced money for school sport, but Cameron learns fast.

While Labour may mock a PM who changes his foreign policy as frequently as his socks, his tough talk on Libya, initially derided, has proved far-sighted now that calls for a no-fly zone are mounting. If the citizens of Benghazi are slaughtered by Gaddafi's troops as the West stands haplessly by, then Cameron will not look the most culpable leader around.

Some in opposition are under no illusion. "Cameron is in a very strong position," says one leading Labour strategist. The same, most critics agree, cannot be said for Nick Clegg, whose latest indignity was a bruising conference defeat on the NHS.

This rout, however, may allow Cameron to do what he should have done months ago and temper Andrew Lansley's misconceived reform agenda. That climbdown would in turn allow Clegg to demonstrate the influence he carries. Even so, few things are going to plan for the Lib Dem leader. His "animating mission", a social mobility strategy due to be unveiled today, has been deferred because some details are yet to be agreed.

So instead of announcing, with the Government social mobility tsar, Labour's Alan Milburn, a plan for intern posts with major companies and a scheme for fair and regulated internships across Whitehall, Clegg can expect only more flak from the Left. In a two-Edded onslaught at the weekend, Balls appeared to veto working with him after the election, while Miliband, in his interview with TheDaily Telegraph, called him "a slightly tragic political figure" and ruled out sharing a pro-AV platform.

This marks quite a change from Miliband's charm offensive of two months ago, in which he said he wanted Labour to be "the standard bearer of Britain's progressive majority" and, reportedly, offered to co-operate with Clegg on issues such as House of Lords reform and the referendum. Now, if the No camp wins, the result will be portrayed as the fault of the Lib Dem leader, who is also facing meltdown in the May elections.

Those close to Clegg say Labour's "ad hominem attacks are for short-term political gain. Long term, it will be bad for them." That may be correct. It is far too early to write off Clegg, who has maintained unexpected unity in his parliamentary party and with whom Miliband may one day have to do business. There is, however, a bigger danger. In an age of consensus politics, for Labour to retreat into its tribal bunker would invite destruction.

More promisingly, the Labour leader has, in recent days, sketched out a vision based around the breaching of "the British promise". Building on research by the Resolution Foundation, he points out that low- and middle-income families, some earning up to £50,000 a year, face a cost-of-living crisis in which their wages and opportunities stagnate. The next generation is seeing its inheritance squandered, both in terms of personal chances and in the ravaging of Britain's treasured institutions, such as libraries and the NHS.

Although friends say the Miliband brothers remain unreconciled, they are thinking along similar lines. Both highlight the need to win back the middle classes and the young as well as the party's disillusioned core vote; both advocate a bottom-up revival, rooted in communities and volunteers. But while David counsels building on New Labour success, Ed is justifiably keener to create some dividing lines with the Blairite past on issues such as crime.

While only the suicidal would urge a Leftwards lurch, more of the same is not a useful prescription either. The two Eds are right to repeat calls for a £2 billion bank bonus to build 25,000 homes and create a youth jobs fund, but such challenges will not determine whether Labour lives or dies. Regaining economic credibility, the top item on the opposition's wish list, must be matched by establishing a credibility of values.

If Labour is to become electable again, it must have something fresh to say not only on schools and health but on immigration, civil liberties, human rights, foreign policy dilemmas, the family and all the toxic issues in which politicians fear to dabble but which ultimately define who has the courage to govern in the interests of all citizens. No opposition can pretend to be a government, but nor can it fudge the defining issues of the age. The outcome of the Arab spring is not going to wait for a Labour Indian summer, if such a balmy season ever rolls around.

The very real fear confronting Labour is that Cameron establishes a stranglehold on power. If Miliband is to stop him, he will have to live dangerously, oppose constructively and offer a concrete basis for hopes and dreams. The choice, as for every leader of the centre-Left, is between rigour and rigor mortis.